Sealing apparatus



Dec. 16, 1958 J. WHITE 2,864,428

SEALING APPARATUS Filed July 8, 1955 FIGI.

3 Sheets-Sheet l Dec. 16, 1958 J. WHITE SEALING APPARATUS 3 Sheets-Sheet 2 Filed July 8, 1955 Dec. 16, 1958 J. WHITE 2,864,428

SEALING APPARATUS Filed July 8, 1955 3 Sheets-Sheet 3 United States Patent Ofii ce 2,864,428 Fatented Dec. 16, 19 58 SEALING APPARATUS James White, Oak Lawn, Ill., assignor, by mesne assignments, to Bemis Bro. Bag Company, St. Louis, Mo., a corporation of Missouri Application July s, 1955, Serial No. 520,692 9 Claims. Cl. 154-42 This invention relates to sealing apparatus, and more particularly to apparatus for sealing heat-sealable sheet material.

Among the several objects of the invention may be noted the provision of a sealing apparatus which is adapted to form astrong narrow continuous longitudinal seam between overlapping portions of heat-scalable sheet material, such as polyethylene; and the provision of'apparatus of this class adapted to form a seam of neat appearance. Essentially, the apparatus of this invention comprises a rotary cylindrical roll, means for guiding the heat-sealable sheet material for travel over the roll with the material arcuately in contact with the roll, and an electrical resist ance heating element having a rigid portion opposed to the periphery of the roll where the overlapping portions of the material travel over the roll. This portion of the element is relatively long in the direction of travel of the material and relatively narrow transverse to the direction of travel of the material. It may either contact the overlapping portions of the material with light pressure, or be positioned out of contact with material but in .close proximity to the material, preferably the latter. The element is fixed against movement in the direction of travel of the material and adapted to be electrically heated to a temperature high enough to vaporize any of the heat- .sealable material that may contact it. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly compn'ses the constructions hereinafter described, the scope of the invention being.

indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

Fig. 1 is a plan view of a sealing apparatus of this invention;

Fig. 2 is a side elevation of Fig. 1;

Fig. 3 is an end elevation of Fig. l as viewed from the right end; Fig. 4 is an enlarged section taken on line 4-4 of Fig. 1;

Fig. 5 is a section taken on line 5-5 of Fig. 4;

Fig. 6 is an enlarged section taken on line 6-6 of Fig. 1;

Figs. 7, 8 and 9 are enlarged sections taken on lines 7-7, 8--8 and 9-9, respectively, of Fig. 6;

Fig. 10 is an enlarged longitudinal section of a heating element per se; and,

Fig. 11 is a section taken on line 11-11 of Fig. 10.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

The apparatus of this invention is particularlyuseful in the manufacture of polyethylene bagsfor longitudinally seaming polyethylene tubing, and is herein described as so used. It will be understood, however, that the apparatus may be used in the manufacture of articles other than bags.

Referring to the drawings,- an apparatus constructedin accordance with this invention is shown to comprise a support including side plates 1 and 3 tied together by four crossbars 5, 7, 9 and 11. A main draw roll 13 has its ends journalled in bearings 15 in the side plates. A handwheel 17 is fixed on one end of the draw roll 13 outward of the respective side plate for manually turning the roll. The roll is power driven by an electric motor 19 via a speed reducer 21, a chain and sprocket drive 23, and an overruning clutch 25. The motor and speed reducer 21 are mounted on a platform 27 which extends between the side plates at the bottom. Bearings 15 are precision bearings, and precision is maintained to insure that the periphery of the draw roll 13 is cylindrical and accurately concentric with respect to the bearings.

The apparatus includes means for guiding continuous 'sheet material for travel over the draw roll 13 with the material arcuately in contact with the draw roll. As shown, this means comprises a pair of rubber-surfaced presser rolls 29 and 31 engaging opposite sides of the draw roll 13. Each presser roll has its ends journalled in bearings 33 slidable in slots 35 in the side plates. Springs 37 bias the presser rolls toward the draw roll 13. Associated with each presser roll is a means for separating it from the draw roll (against the spring bias) to simplify threading of the material between the presser rolls and the draw roll. As shown, this means comprises a shaft 39 journalled at its ends in bushings 40 in the side plates and having a handle 41 at one end. Eccentrics 43 are fixed on the shaft adjacent the inside faces of the side plates (see Figs. 4 and 5). Links 45 have openings 47 at one end receiving the eccentrics and slots 49 at the other end receiving the shaft ends of the presser roll. By turning the shaft 39 for each presser roll in one direction, the presser roll is pulled away from the draw roll, and by returning the shaft in the opposite direction, the presser roll is released to be spring-biased against the draw roll.

I Latching means for the shaft 39 is shown to comprise a spring-biased ball 5%) carried by the bushing 40 engageable in notches 51 in the hub of the handle. Rearward and forward idler guide rolls 52 and 53 are journalled at their ends in bearings 55 in the side plates.

The cross bar 5 extends above the rearward presser roll 29. It has a groove 57 and a slot 59 through the bottom of the groove. A U-shaped block 61 has its base slidable in the groove transversely of the apparatus. The block is held in the groove by clamp strips 63. A stud 64 extends from the bottom of the block through the slot 59 and has a nut 65 at its outer end. This nut is in threaded engagement with a threaded shaft 67 having its ends journalled in bearings 69 in the side plates. Shaft '67 has a knob 71 on one end for turning it in one direction or the other to slide the block 61 in one direction or'the other on the bar 5.

An electrically conductive plate 73 is attached to a pair of rods 75 at one end of the rods. These rods 75 are slidable in openings 77 in the sides of the U-shaped block 61 in a radial plane with respect to the draw roll 13. Fixed to the other and outer end of the rods 75 is a tie plate 79. Adjustably threaded in a tapped hole 81 in the tie plate 79 is a stop screw 83 having its inner end engageable with the block 61 (see Figs. 6 and 8). Springs 85 surrounding the rods 75 biasthe assembly comprising plate 73, the rods 75 and plate 79 outward away from the draw roll 13. An air cylinder 87 is fixed tothe U-shaped block 61 in the space between its sides. This cylinder has a piston 89 therein and a piston rod 91 extending downward to a connection at 93 with the plate 73. The latter constitutes a holder for a rigid elongate electrical heating element generally designated 95. v

The element 95, as shown in Figs. 10 and 11, comprises a length of resistance wire 97, such as Nichrome wire, in a sheath 99 of noncorrosive metal, for example, a stainless steel such as Inconel, with insulation 101 between the wire 97 and the sheath 99. The wire 97 has one end 103 projecting from the sheath 99 and is in electrical contact with the sheath at its other end as indicated at 105. At this-end of the element, the sheathis provided with a shoe 107 of, stainless steel, having a narrow face 109 which is curved transversely with respect to the length of the element 95 (see Fig. 11) and also curved lengthwise of the element 95 (see Fig. to follow the curvature of the draw roll 13. The shoe isadapted electrically to be heated to a temperature high enough to vaporize any of the heat-sealable materials such as polyethylene that may contact it, for example, from 600 F. to 1500 F. The element 95 is mounted in electrically conductive pins 111 and 113which extend from the plate 73 toward thev periphery of the draw roll 13 located in a planegenerally at right angles to the axis of the draw roll 13. A set screw 114 (see Fig. 10) holds the element in place. The element extends generally in tangential direction with respect to the roll 13.

The apparatus is shown in Figs. 6-8 as being used for longitudinally seaming polyethylene tubing 115. This tubing is formed from a flat web of polyethylene in a conventional type of tuber, a portion of which is shown in Figs. 7 and 8. As shown therein, the web is formed into tubing around upper and lower former blades 117 and 119, respectively, and the tubing is formed with gussets 121 by means of intucking blades 123. In the formation of the tubing, the margins 125 and 127 of the web are brought into overlapping relation as shown in Fig. 7. The tubing travels between the rearward presser roll 29 and the draw roll 13, thence around the draw roll and between the shoe 107 of the element 95 and the draw roll, and thence between the forward presser roll 31 and the draw roll, with the overlapping margins 125, 127 on the outside. The U-block 61 is transversely adjusted by turning the knob 71 so that the shoe 107 of the element 95 is opposed to the overlapping margins 125 and 127 of the polyethylene travelling over the draw roll 13.

During the operation of the apparatus, plate 73 is held in its inner position by air in the cylinder 87. This inner position of plate 73 is determined by engagement of the end of the screw. 83 with the block 61. The screw 83 is preferably so adjusted that, with the plate 73 in its inner position, face 109 of shoe 107 is slightly out of contact (by .015 inch, for example) with the polyethylene (see Fig. 8, wherein this spacing is exaggerated). Current is supplied to the element 95 by means of a positive wire 129 attached to the projecting end 103 of the resistance wire 97 and a ground wire 131 attached to the plate 73, the current being sufficient to heat the shoe to a temperature of from about 600 F. to 1500 F., and preferably about 1200" F., for polyethylene. The temperature is sufficiently high to vaporize any polyethylene that may contact the shoe.

A flexible tongue 133 is used between the walls of the tubing to prevent any sealing together of the walls of the tubing. This tongue may consist, for example, of a strip of material made from glass fibers impregnated with polymerized tetrafluoroethylene sold under the trade name Teflon, and having a coating of Teflon on both sides, the Teflon coating being omitted, however, on one side of the strip in the region under the shoe 107. The tongue 133, as shown in Fig. 6, is secured at one end 135 to the upper former blade 117 and extends between the rearward presser roll 29 and the draw roll 13 together with and inside the tubing, extending about one inch, for example, beyond the shoe 107.

As the overlapping margins 125 and 127 of the tubing travel under the heated shoe 107, the polyethylene under the shoe is melted and a continuous strong narrow longitudinal heat-sealed seam of neat appearance is formed. Any melted polyethylene that may contact the shoe is substantially instantly vaporized.

In view of the above, it will be seen that the several '4 objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative andnot in a limiting sense.

I claim:

1. Apparatus for forming a longitudinal heat-sealed seam between overlapping portions of continuous heatsealable sheet material, comprising a rotary cylindrical roll, means for guiding the material for travel over the roll with the material arcuately in contact with the roll, and an electrical resistance heating element having a rigid portion opposed to the periphery of the roll where the overlapping portions of the material travel over the roll, said portion being relatively long in the direction of travel of the material and relatively narrow transverse to the direction of travel of the material, and said element being fixed against movement in the direction of travel of the material and adapted electrically to be heated to a temperature high enough to vaporize any heat-scalable material that may contact it.

2. Apparatus as set forth in claim 1 wherein said element is mounted for adjustment toward and away from the roll.

3. Apparatus for forming a longitudinal heat-sealed seam between overlapping portions of continuous heatsealable sheet material, comprising a rotary cylindrical roll, means for guiding the material for travel over the roll with the materialarcuately in contact with the roll, an elongate rigid electrical resistance heating element located in a plane generally at right angles to the axis of the roll and opposed to the periphery of the roll where the overlapping portions of the material travel over the roll, said element being fixed against movement in the direction of travel of the material and adapted electrically to be heated to a temperature high eough to vaporize any heat-sealable material that may contact it, said element having. a face opposed to the roll which is relatively narrow in respect to the length of the element.

4. Apparatus as set forth in claim 3 wherein said element is mounted for adjustment in said plane toward and away from the roll.

5. Apparatus for forming a longitudinal heat-sealed seam between overlapping portions of continuous heatsealable sheet material, comprising a support, a rotary cylindrical roll carried by the support for rotation on a fixed axis, means carried by the support for guiding the material for travel over the roll with the material arcuately in contact with the roll, a holder carried by the support for movement toward and away from the periphery of the roll where the overlapping portions of the material travel over the roll, an elongate rigid electrical resistance heating element carried by the holder in a plane generally at right angles to the axis of the roll, said element being fixed against movement in the direction of travel of the material and adapted electrically to be heated to a temperature high enough to vaporize any heat-sealable material that may contact it, said element having a face opposed to the periphery of the roll which is relatively narrow in respect to the length of the element, and means for moving the holder toward and away from the roll.

6. Apparatus as set forth in claim 5 wherein there is provided adjustable stop means for limiting the movement of the holder toward the roll for adjustably positioning the element at different selected distances from the periphery of the roll.

7. Apparatus for forming a longitudinal seam between overlapping portions of continuous heat-sealable sheet material, comprising a support, a rotary cylindrical roll carried by the support for rotation on a fixed axis, means, carried bythe support for guiding the material for travel over the roll with the material arcuately in contact with the roll, a holder carried by the support for movement toward and away from the periphery of the roll and for movement parallel to the roll, an elongate rigid electrical resistance heating element carried by the holder in a plane generally at right angles to the axis of the roll, said element being fixed against movement in the direction of travel of the material and adapted electrically to be heated to a temperature high enough to vaporize any heat-scalable material that may contact it, said element having a face opposed to the periphery of the roll which is relatively narrow in respect to the length of the element, means for moving the holder toward and away from the roll, and adjustable stop means for limiting the movement of the holder toward the roll.

8. Apparatus for forming a lonigtudinal seam between overlapping portions of continuous heat-scalable sheet material comprising a support, a rotary cylindrical draw roll carried by the support for rotation on a fixed axis, means for driving the draw roll, presser rolls carried by the support cooperable with the draw roll for guiding the material for travel over the draw roll with the material arcuately in contact with the draw roll, a block carried by the support for movement parallel to the draw roll, a holder carried by the block for movement toward and away from the periphery of the draw roll, a rigid elongate electrical resistance heating element carried by the holder extending generally tangentially with respect to the draw roll, said element being fixed against movement in the direction of travel of the material and adapted electrically to be heated to a temperature high enough to vaporize any heat-scalable material that may contact it, said element having an end portion opposed to the periphery of the draw roll, said end portion having a face which is relatively narrow in respect to the length of the element, means carried by the block for moving the 6 holder toward and away from the roll, and adjustable stop means movable with the holder and engageable with the block for limiting the movement of the holder toward the draw roll.

9. In combination, means for forming a web of heatsealable material into tubing wherein the margins of the web overlap, and apparatus for forming a longitudinal seam between said overlapping margins comprising a rotary cylindrical roll, means for guiding the tubing for travel over the roll with the tubing arcuately in contact with the roll and with said overlapping margins on the outside, an electrical resistance heating element having a rigid portion opposed to the periphery of the roll where said overlapping margins travel over the roll, said portion being relatively long in the direction of travel of the tubing and relatively narrow transverse to the direction of travel of the tubing, said element being fixed against movement in the direction of travel of the material and adapted electrically to be heated to a temperature high enough to vaporize any heat-scalable material that may contact it, and a flexible heat-insulating tongue secured at one end to said forming means and adapted to extend within the tubing around said roll for preventing wall-to-wall sealing of the tubing.

References Cited in the file of this patent UNITED STATES PATENTS 2,227,497 Hallman Jan. 7, 1941 2,343,975 Hosfield Mar. 14, 1944 2,591,383 Spalding Apr. 1, 1952 2,660,219 Haas et a1. Nov. 24, 1953 2,680,471 Mercer June 8, 1954 2,718,915 Piazze Sept. 27, 1955 2,780,275 Rusch et a1 Feb. 5, 1957 2,788,838 Crabbe et a1. Apr. 16, 1957 

